Picture coding method, picture decoding method, picture coding apparatus, picture decoding apparatus, and program thereof

ABSTRACT

A picture coding method of the present invention codes a picture signal and a ratio of a number of luminance pixels and a number of chrominance pixels for the picture signal, and then one coding method out of at least two coding methods is selected depending on the ratio. Next, data related to a picture size is coded in accordance with the selected coding method. The data related to the picture size indicates a size of the picture corresponding to the picture signal or an output area, which is a pixel area to be outputted in decoding in a whole pixel area coded in the picture signal coding.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a picture coding method for efficientlycompressing moving pictures and to a picture decoding method forcorrectly decoding the compressed moving pictures.

(2) Description of the Related Art

In the age of multimedia which integrally handles audio, video and otherpixel values, existing information media (e.g., newspaper, magazine,television, radio, telephone and other means) through which informationis conveyed to people, has recently been included in the scope ofmultimedia. Generally, multimedia refers to something that isrepresented by associating not only characters, but also graphics, audioand especially pictures and the like together. However, in order toinclude the aforementioned existing information media into the scope ofmultimedia, it is necessary to represent such information in digitalform.

However, when calculating the amount of information contained in each ofthe aforementioned information media as the amount of digitalinformation, the amount of information per character is 1 to 2 bytes inthe case of characters, while the amount of information to be requiredis 64 Kbits per second in the case of audio (telephone quality), and 100Mbits per second in the case of moving pictures (current televisionreception quality). Therefore, it is not realistic for theaforementioned information media to handle such an enormous amount ofinformation as it is in digital form. For example, although video phonesare already in practical use by using Integrated Services DigitalNetwork (ISDN) which offers a transmission speed of 64 Kbits/s to 1.5Mbits/s, it is not possible to transmit video of televisions and camerasdirectly through ISDN.

In this circumstance, information compression techniques have becomerequired, and moving picture compression techniques compliant with H.261and H.263 standards recommended by ITU-T (InternationalTelecommunication Union-Telecommunication Standardization Sector) areemployed for video phones, for example. Moreover, according toinformation compression techniques compliant with the MPEG-1 standard,it is possible to store picture information into an ordinary music CD(compact disc) together with audio information.

Here, MPEG (Moving Picture Experts Group) is an international standardon compression of moving picture signals standardized by ISO/IEC(International Organization for Standardization, InternationalElectrotechnical Commission), and MPEG-1 is a standard for compressingtelevision signal information approximately into one hundredth so thatmoving picture signals can be transmitted at a rate of 1.5 Mbit/s.Furthermore, since the intended quality is a middle-quality realized bya transmission speed of chiefly about 1.5 Mbit/s in MPEG-1 standard,MPEG-2, which has been standardized with a view to satisfyingrequirements for further improved picture quality, allows datatransmission equivalent in quality to television broadcasting throughwhich moving picture signals are transmitted at a rate of 2 to 15Mbit/s. Moreover, MPEG-4 has been standardized by a working group(ISO/IEC JTC1/SC29/WG11) which promoted the standardization of MPEG-1and MPEG-2. MPEG-4, which provides a higher compression ratio than thatof MPEG-1 and MPEG-2 and which enables an object-basedcoding/decoding/operation, is capable of providing a new functionalityrequired in this age of multimedia. At the beginning stage ofstandardization, MPEG-4 was aimed at providing a low bit rate codingmethod, but it has been extended as a standard supporting more generalcoding that handles interlaced images as well as high bit rate coding.Currently, an effort has been made jointly by ISO/IEC and ITU-T forstandardizing MPEG-4 AVC and ITU-T H.264 as picture coding methods ofthe next generation that offer a higher compression ratio. And these areapproved as international standards as of June 2004.

As for picture coding, coding is generally performed per block, andmostly the size of the block is 16 pixels per unit. Actually the picturesize allowing coding is in multiples of 16, which is a multiple of thenumber of pixels of per block. However, for example, the number ofpixels for picture signals of HDTV is 1920 in a horizontal and 1080 invertical. However, 1080 is not a multiple of 16 inconveniently. Becauseof this, coding is performed per block, which results in clipping out ofthe coded (decoded) picture for outputting (display on a screen).

FIG. 1 is a drawing to describe a display area of pictures. In FIG. 1,the number of horizontal pixels is represented by MBWidth and the numberof vertical pixels is represented by MBHeight for coding (encoding)pictures. And also a black circle denotes a pixel outputted by decodingapparatus and white circle denotes a pixel to be coded but not outputtedby decoding apparatus. In order to indicate pixels to be outputted amongthe coded pixels, the number of horizontal pixels, which is the Width ofthe area to be outputted, and the number of vertical pixels, which isthe Height of the area to be outputted are represented by the number ofleft pixels LCrop, right pixels RCrop, top pixels TCrop and bottompixels BCrop. Here following equalities can be obtained:Width=MBWidth−Lcrop−RcropHeight=MBHeight−TCrop−Bcrop.

Picture signals are usually represented by a luminance and achrominance. A human's ability for discriminating resolution ofchrominance is relatively weak comparing to discriminating of luminance.Therefore, compressing efficiency is improved by making the number ofluminance smaller than the number of chrominance. Generally the ratio ofthe number of luminance to the number of chrominance is relatively smallfor general consumer products while the ratio is close to one forprofessional products.

FIG. 2A, FIG. 2B and FIG. 2C are drawings to show color format ofpictures. In the drawings a white circle denotes a pixel location ofluminance and a black circle denotes a pixel location of chrominance.FIG. 2A is 4:2:2 color format, FIG. 2B is 4:2:2 color format and FIG. 2Cis 4:4:4 color format.

It should be noted that in the case of a component picture signalrepresented by RGB, wherein as green includes a large amount ofluminance components, a white circle denotes G (green) and a blackcircle denotes R (red) and B (blue).

FIG. 3 is a drawing to show a data structure of bitstream. The bitstreamStr is comprised of PixelData which is each pixel value datum, andCommonData which is a common data of frame or plural of frames. TheCommonData includes a color format ChromaFormat and an output areacoding information CropData. The color format ChromaFormat indicates,for example, any one of 4:2:0, 4:2:2 or 4:4:4. The output area codinginformation CropData indicates, for example, the number of left pixelsLCrop, right pixel RCrop, top pixels TCrop and bottom pixels BCrop.

FIG. 4A and FIG. 4B are drawings to show a variable-length code table.FIG. 4A is an example of a table of variable-length code table of colorformat ChromaFormat. FIG. 4B shows an output area coding informationCropData. It is an example of a variable-length code table for codingthe each value (Value) of the number of left pixels LCrop, right pixelsRCrop, top pixels TCrop and bottom pixels BCrop. When the value (Value)is larger, the code length is longer, and more number of bits isnecessary.

(see ITU-T Rec. H264|ISO/IEC 14496-10 version 1 “Informationtechnology—Coding of audio-visual objects—Part 10: Advanced videocoding”, non-patent literature 1)

Now, the number of chrominance pixels is less than the number ofluminance pixels. Thus, the number of luminance pixels which can beoutputted is actually an integral multiple. For example in FIG. 2A, twopixels in horizontal direction and two pixels in vertical direction ofluminance corresponds to one pixel of chrominance, and the number ofluminance pixels and the location of pixels that can be outputted aremultiples of two in both horizontal and vertical directions. Because ofthis, each value (Value) of the number of left pixels LCrop, rightpixels RCrop, top pixels TCrop and bottom pixels BCrop becomes an evennumber. On the other hand, in the case of FIG. 2C, either an even numberor an odd number can be possible. However, in the case that the evennumber is the only possible case, if the values are coded by the way inFIG. 4B substantially, the coding efficiency can not be expected, sincethe odd numbers, not to be coded, are also included in the case of FIG.2A.

If a coding supposing only the color format ChromaFormat like FIG. 2A(for example the non-patentable literature 1), the number of left pixelsLCrop, right pixels RCrop, top pixels TCrop and bottom pixels BCrop aremultiplied by ½ respectively, and then the value is coded using thetable in FIG. 4B. By this way, for example RCrop=4 needs originally 5bits of “00101”, but now coding can be possible with 3 bits of “011”from RCrop/2=2, as a result, 2 bits can be saved. However, only evenposition can be displayed with this way in the case like FIG. 2C.

BRIEF SUMMARY OF THE INVENTION

The object of the present invention is to provide a picture codingmethod, a picture decoding method, a picture coding apparatus, a picturedecoding apparatus, and a program thereof for coding data related to apicture size with less number of bits without deteriorating accuracy ofoutput pixel to be presented.

In order to achieve the object, the picture coding method is for codinga picture signal, coding a ratio of the number of luminance pixels tothe number of chrominance pixels for the picture signal, selecting onecoding method out of at least two coding methods depending on the ratioand coding a data related to a picture size in accordance with theselected coding method.

According to this construction, the data related to picture size iscoded by the selected coding method depending on the ratio of the numberof luminance pixels to chrominance pixels, the coding, therefore, can beexecuted with less number of bits without deteriorating the accuracy ofoutput pixel to be presented.

Here, the data related to the picture size may indicate the size of apicture corresponding to the picture signal.

According to this construction, coding can be executed with less numberof bits without deteriorating the accuracy of output pixel being able tobe presented for the picture size corresponding to the picture signal.

In the selecting of the coding method, in a case where a ratio of thenumber of horizontal luminance pixels to the number of horizontalchrominance pixels is M:1, a coding method coding 1/M of the number ofhorizontal pixels may be selected, the horizontal luminance pixels andthe horizontal chrominance pixels being included in the picture signal.

According to this construction, a variable length code tablecorresponding to 1/M variable length coding instead of a variable lengthcode table corresponding to variable length coding of M can be used.Thereby coding 1/M of the number of horizontal pixels to a variablelength code with less number of bits can be executed. For example, inthe case where variable length coding is executed for the number ofhorizontal pixels, the coding is executed using the part of 1/M of thevariable length code table with short code length in the head in thevariable length code table indicating M of variable length code, thusthe coded variable length code of the number of horizontal pixels can beshortened.

In the selecting of the coding method, in a case where a ratio of thenumber of vertical luminance pixels to the number of verticalchrominance pixels is N:1, a coding method coding 1/N of the number ofvertical pixels may be selected, the vertical luminance pixels and thevertical chrominance pixels being included in the picture signal.

According to this construction, a variable length code tablecorresponding to 1/N variable length coding instead of a variable lengthcode table corresponding to variable length coding of N can be used.Thereby coding the value of 1/N of the number of vertical pixels to avariable length code with less number of bits can be executed. Forexample, in the case where variable length coding is executed for thenumber of vertical pixels, the coding can be executed using the part of1/N of the variable length code table with short code length in the headin the variable length code table indicating N of variable length code.

Here, the data related to the picture size may indicate an output areain a whole pixel area coded in the coding of a picture signal, theoutput area being a pixel area to be outputted in decoding.

According to this construction, in the case where the size of the codedwhole pixel area is larger than the output area which is a pixel area tobe outputted in decoding, coding can be executed with less number ofbits without deteriorating the accuracy of output area.

Here, the data related to the picture size includes a bottom crop valueand a right crop value, the bottom crop value may show the number ofpixels from the bottom end of the whole pixel area to the bottom end ofthe output area, the right crop value may show the number of pixels fromthe right end of the whole pixel area to the right end of the outputarea.

The data related to the picture size further includes a top crop valueand a left crop value, the top crop value may show the number of pixelsfrom the top end of the whole pixel area to the top end of the outputarea, the left crop value may show the number of pixels from the leftend of the whole pixel area to the left end of the output area.

According to this construction, it is possible to improve codingefficiency further because the coding is executed for the crop value oftop, bottom, left and right, having values that are smaller than thenumber of horizontal and vertical pixels of output area by the selectedcoding method.

Here, in the selecting of the coding method, in a case where a ratio ofthe number of horizontal luminance pixels to the number of horizontalchrominance pixels is M:1, a coding method coding 1/M of each value ofthe left crop value and the right crop value may be selected, thehorizontal luminance pixels and the horizontal chrominance pixels beingincluded in the picture signal.

According to this construction, a variable length code tablecorresponding to 1/M variable length coding instead of a variable lengthcode table corresponding to variable length coding of M can be used.Thereby each value of 1/M of left/right crop values can be coded tovariable length code with less number of bits. For example, in the casewhere variable length coding is executed for each value of 1/M ofleft/right crop values, the coding is executed using the part of 1/M ofthe variable length code table with short code length in the head in thevariable length code table indicating M of variable length code, thusthe coded variable length code of the number of horizontal pixels can beshortened.

Here, in the selecting of the coding method in a case where a ratio ofthe number of vertical luminance pixels to the number of verticalchrominance pixels is N:1, a coding method coding 1/N of each value ofthe top crop value and the bottom crop value may be selected, thevertical luminance pixels and the vertical chrominance pixels beingincluded in the picture signal.

According to this construction, a variable length code tablecorresponding to 1/N variable length code instead of a variable lengthcode table corresponding to variable length code of N can be used.Thereby coding the each value of 1/N of the top and the bottom cropvalues to a variable length code with less number of bits can beexecuted. For example, in the case where variable length coding isexecuted for the each value of 1/N of top and bottom crop values, thecoding is executed using the part of 1/N of the variable length codetable with short code length in the head in the variable length codetable indicating N of variable length code, thus the coded variablelength code of the number of vertical pixels can be shortened.

Further, the picture decoding method, the picture coding apparatus, thepicture decoding apparatus and the program thereof have the sameconstructions as mentioned above.

The disclosure of Japanese Patent Application No. 2004-238431 filed onAug. 18, 2004 including specification, drawings and claims isincorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings identified below thatillustrate a specific embodiment of the invention.

FIG. 1 is a drawing to describe a display area of pictures.

FIG. 2A, FIG. 2B and FIG. 2C are drawings to show a color format ofpictures.

FIG. 3 is a drawing to show a data structure of a bitstream.

FIG. 4A and FIG. 4B are drawings to show a variable-length code table.

FIG. 5 is a block diagram to show a structure of a picture codingapparatus of the present invention.

FIG. 6 is a block diagram to show a structure of a picture decodingapparatus of the present invention.

FIG. 7A and FIG. 7B are flowcharts to show picture coding methods of thepresent invention.

FIG. 8A and FIG. 8B are flowcharts to show picture decoding methods ofthe present invention.

FIG. 9A, FIG. 9B and FIG. 9C are drawings to show recording media suchas flexible disc.

FIG. 9A shows an example of a physical format of flexible disc as arecording medium.

FIG. 9B shows a front view of an appearance, a section structure for aflexible disc and a flexible disc.

FIG. 9C shows a structure for recording and replaying of above saidprogram on a flexible disc.

FIG. 10 shows a block diagram to show a whole structure of a contentproviding system.

FIG. 11 shows an appearance of a cellular phone.

FIG. 12 is a block diagram to show a structure of a cellular phone.

FIG. 13 shows an example of a digital broadcasting system.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter the embodiment of the present invention is described usingFIG. 5 to FIG. 13.

FIG. 5 is a block diagram to show a structure of a picture codingapparatus of the present invention. The pixels values of input pictureVin are coded using orthogonal transformation, quantization, variablelength coding, motion compensation and so on by pixel coding unit EncU.The coded input picture Vin is outputted as coded picture data DataV.The output area Area specifying the area of pixels to be outputted by apicture decoding apparatus is inputted from outside into an output areainformation converting unit AreaEncU, and the output area informationconverting unit AreaEncU coverts output area Area into output areainformation Crop depending on color format ChromaFormat inputted fromoutside.

For example, in the case where the color format ChromaFormat indicatesthat the ratio of pixel numbers of luminance to chrominance is M:1 inhorizontal direction and N:1 in vertical direction, LCrop, RCrop, TCropand BCrop representing output area Area are converted into LCrop/M,RCrop/M, TCrop/N and BCrop/N respectively. These represent the outputarea information Crop. The output area information coding unit CropEncUcodes the output area information Crop by such as the variable lengthcode table in FIG. 4B. And then the coded output area information Cropis outputted as the output area coding information CropData. On theother hand, the color format coding unit ChromaFormatEncU codes thecolor format ChromaFormat by such as the variable length code table inFIG. 4A. And then the coded color format ChromaFormat is outputted asthe color format coding information ChromaFormatData. A multiplexingunit MuxU multiplexes the color format coding informationChromaFormatData, the output area coding information CropData and thecoding picture data, and outputs the multiplexed data as a bitstreamStr.

Conventionally the output area coding information CropData has beencoded by a fixed method irrespective of color format ChromaFormat. Inthe present invention the output area coding information CropData iscoded based on color format ChromaFormat. In this coding method, in thecase where, the ratio of the number of horizontal pixels of luminance tochrominance is M:1, the value of the output area coding informationCropData is multiplied by 1/M, and the 1/M of output area codinginformation CropData is coded. This method saves a necessary number ofbits for coding, since the size of the output area coding informationCropData is decreased. In the case where the ratio of the number ofhorizontal pixels of luminance to chrominance is M:1, the number ofluminance pixels is multiple of M. According to the coding ofembodiment, the output area can be presented accurately with M pixelunit that is the minimum unit of the number of luminance pixels.

Similarly, in the case where, the ratio of the number of vertical pixelsof luminance to chrominance is N:1, the value of the output area codinginformation CropData is multiplied by 1/N, and the 1/N of output areacoding information CropData is coded. This method saves a necessarynumber of bits for coding, since the size of the output area codinginformation CropData is decreased. In the case where the ratio of thenumber of vertical pixels of luminance to chrominance is N:1, the numberof luminance pixels is multiple of N. According to the coding ofembodiment, the output area can be presented accurately with N pixelunit that is the minimum unit of the number of luminance pixels.

As mentioned hereinbefore, it is possible to code the output area codinginformation CropData with less number of bits without deterioratingaccuracy of output pixel to be represented, and the practical value ishigh.

It should be noted that the output area information Crop, indicated byLCrop, RCrop, TCrop and BCrop, and Width and Height, may be used as apart of data substitutively. Additionally, in the case where LCrop andTcrop of the output area are zero, only RCrop and BCrop may be coded asoutput information Crop Data.

Furthermore, the picture size of the whole pixel area to be coded, thatis the number of horizontal pixels MBWidth and the number of verticalpixels MBHeight shown in FIG. 1, may be coded similarly together withoutput area information or substitutively as a data related to thepicture size.

FIG. 6 is a block diagram to show a structure of a picture decodingapparatus of the present invention. The bitstream Str is separated intoa color format coding information ChromaFormatData, an output areacoding information CropData and a coding picture data DataV in thedemultiplexing unit DeMuxU. The coding picture data DataV is decodedusing anti-orthogonal transformation, anti-quantization, variable lengthdecoding, motion compensation and so on by pixel decoding unit DecU. Thepixels values obtained by the decoding are outputted as decoded picturedata DecV. The color format decoding unit ChromaFormatDecU decodes thecolor format coding information ChromaFormatData by such as the variablelength code table in FIG. 4A. And then the decoded color format codinginformation ChromaFormatData is outputted as color format ChromaFormat.Similarly the output area information decoding unit CropDec U decodesthe output area coding information CropData by such as the variablelength code table in FIG. 4B. And then the decoded output area codinginformation CropData is outputted as output area information Crop. Theoutput area specifying unit AreaDecU converts the output areainformation Crop into the output area Area depending on color formatChromaFormat.

For example, in the case where color format ChromaFormat indicates thatthe ratio of the number of pixels of luminance to chrominance is M:1 inhorizontal direction and N:1 in vertical direction, since the outputarea information Crop represents LCrop/M, RCrop/M, TCrop/N and BCrop/N,LCrop, RCrop, TCrop and BCrop representing the output area Area can beobtained by multiplying by M or N respectively. The output areaextracting unit CropU extracts the area indicated by output area Areaout of decoding picture data DecV, and outputs as output picture Vout.

It should be noted that the output area information Crop are indicatedby LCrop, RCrop, TCrop and BCrop, and Width and Height may be used as apart of data substitutively. Additionally, in the case where LCrop andTcrop of the output area are zero, only TCrop and BCrop may be decodedout of output information CropData.

Furthermore, the picture size of the whole pixel area to be coded, thatis the number of horizontal pixels MBWidth and the number of verticalpixels MBHeight shown in FIG. 1 may be decoded similarly together withoutput area information or substitutively as a data related to thepicture size.

FIG. 7A is a flowchart to show a picture coding method of the presentinvention and to show a procedure of a picture coding method as shown ina block diagram of the picture coding apparatus of the present inventionin FIG. 5.

First the output area Area and the color format ChromatFormat areobtained from outside (Step 10). The derivation process for output areainformation Crop is changed depending on the color format ChromaFormat,which is either 4:2:0, 4:2:2 or 4:4:4 (Step 11). In the case where colorformat ChromaFormat is 4:2:0, width (value in horizontal direction) andheight (value in vertical direction), which are contained in the outputarea information, are multiplied by ½ respectively, and the result ofthe multiplication by ½ is used as output area information Crop (Step12). In the case where color format ChromaFormat is 4:2:2, only width(value in horizontal direction), which is contained in the output areainformation, is multiplied by ½, and the result of the multiplication by½ is used as output area information Crop (Step 13). After an inputpicture Vin is coded (Step 14), the color format ChromaFormat and outputarea information Crop are coded (Step 15).

It should be noted that Step 14 may be performed before Steps 10 and 11,and the case that Step 14 is performed before Step 11 is shown in FIG.7B.

Additionally, the codings of the color format ChromaFormat and theoutput area information Crop (Step 15) may be executed before the codingof the input picture Vin (Step 14). In that case, Step 14 is executedimmediately after Step 15 in the flowcharts of FIG. 7A and FIG. 7B.

Besides, in the embodiment, it is exemplified that the color formatsChromaFormat are 4:2:0, 4:2:2 and 4:4:4 only. However, in the case wherethe ratio of the number of pixels of luminance to chrominance is M:1 inhorizontal direction and N:1 in vertical direction, the width can bemultiplied by 1/M instead of ½ and the height can be multiplied by 1/Ninstead of ½ for functioning practically.

Furthermore, the picture size of the whole pixel area to be coded, thatis the number of horizontal pixels MBWidth and the number of verticalpixels MBHeight shown in FIG. 1, may be coded similarly together withoutput area information or substitutively as a data related to thepicture size.

FIG. 8A is a flowchart to show a picture decoding method of the presentinvention and is showing the procedure of the picture decoding method asshown in the block diagram of the picture decoding method in FIG. 6.

First the output area information Crop and the color format ChromaFormatare decoded (Step 20). The decoding process of the output areainformation Crop is changed depending on the color format ChromaFormat,which is either 4:2:0, 4:2:2 or 4:4:4 (Step 21). In the case where colorformat ChromaFormat is 4:2:0, width (value in horizontal direction) andheight (value in vertical direction), which are contained in the outputarea information indicated in output area information Crop, aremultiplied by 2 respectively, and the result of the multiplication by 2is used as output area Area (Step 22). In the case where the colorformat ChromaFormat is 4:2:2, only width (value in horizontaldirection), which is contained in output area information indicated inoutput area information Crop, is multiplied by 2, and the result of themultiplication by 2 is used as output area Area (Step 23). After thepicture signal is decoded out of the bitstream Str (Step 24), a part ofthe decoded picture is extracted depending on the output area Area, andoutputted as an output picture Vout (Step 25).

It should be noted that Step 24 may be performed before Steps 20 and 21,and the case that Step 24 is performed before Step 21 is shown in FIG.8B.

Besides, in the embodiment, it is exemplified that the color formatsChromaFormat are 4:2:0, 4:2:2 and 4:4:4 only. However, in the case wherethe ratio of the number of pixels of luminance to chrominance is M:1 inhorizontal direction and N:1 in vertical direction, the width can bemultiplied by M instead of 2 and the height can be multiplied by Ninstead of 2 for functioning practically.

Furthermore, the picture size of the whole pixel area to be coded, thatis the number of horizontal pixels MBWidth and the number of verticalpixels MBHeight shown in FIG. 1 may be decoded similarly together withoutput area information or substitutively as a data related to thepicture size.

Moreover, if a program for realizing the picture coding method and thepicture decoding method mentioned above are recorded on a recordingmedium such as a flexible disk, it is possible to easily perform theprocessing presented above in an independent computer system.

FIG. 9A, FIG. 9B and FIG. 9C are diagrams illustrating a recordingmedium that stores a program for realizing the picture coding method andthe picture decoding method according to the above-mentioned embodiment.

FIG. 9B shows a front view of an appearance, a section structure for aflexible disc and a flexible disc, FIG. 9A shows an example of aphysical format of flexible disc as a recording medium. The flexibledisk FD is contained in a case F, and plural of tracks Tr are formedconcentrically on the surface of the flexible disk FD from peripherytoward inner periphery, each track being divided into 16 sectors Se inthe angular direction. Therefore, in the flexible disk storing theabove-mentioned program, the picture coding method and the picturedecoding method as such programs are recorded in an area allocated forit on the flexible disk FD.

Further, FIG. 9C shows a structure for recording and replaying of abovesaid programs into a flexible disc FD. When the above programs torealize the picture coding method and the picture decoding method are tobe recorded on the flexible disk FD, such programs shall be writtenusing computer system Cs via a flexible disk drive FDD. Meanwhile, whenthe picture coding method and the picture decoding method, which realizethe picture coding method and the picture decoding method by theprograms in flexible disc FD, are to be constructed in the computersystem, the program shall be read out from flexible disk FD via theflexible disk drive FDD and then transferred to computer system Cs.

It should be noted that a flexible disc is exemplified as a recodingmedium in the above-mentioned description, but an optical disc also canbe used likewise. Further recording media are not limited to aboveexamples, but any program recordable media such as an IC card, a ROMcassette and so on can be practical.

The following describes application examples of the picture codingmethod and the picture decoding method as shown above as well as asystem employing them.

FIG. 10 shows a whole structure of a content providing system ex100 thatrealizes a content providing service. The area for providing acommunication service is divided into cells of desired size, and basestations ex107 to ex110, which are fixed wireless stations, are placedin the respective cells.

In this content providing system ex100, devices such as a computerex111, a PDA (Personal Digital Assistant) ex112, a camera ex113, acellular phone ex114, and a camera-equipped cellular phone ex115 arerespectively connected to Internet ex101 via an Internet serviceprovider ex102, a telephone network ex104, and base stationsex107˜ex110.

However, content providing system ex100 is not limited to thecombination as shown in FIG. 10, and may be connected to a combinationof any of them. Also, each of the devices may be connected directly totelephone network ex104, not via base stations ex107 to ex110, which arefixed wireless stations. Camera ex113 is a device such as a digitalvideo camera capable of taking moving pictures. The cellular phone maybe a cellular phone of a PDC (Personal Digital Communication) system, aCDMA (Code Division Multiple Access) system, a W-CDMA (Wideband-CodeDivision Multiple Access) system or a GSM (Global System for MobileCommunications) system, a PHS (Personal Handyphone system) or the like,and may be any one of these.

Furthermore, a streaming server ex103 is connected to camera ex113 viabase station ex109 and telephone network ex104, which enables livedistribution or the like based on coded data transmitted by a user usingcamera ex113. Either camera ex113 or a server and the like capable ofdata transmission processing may code the data taken. Also, movingpicture data taken by a camera ex116 may be transmitted to streamingserver ex103 via computer ex111. Camera ex116 is a device such as adigital camera capable of taking still pictures and moving pictures. Inthis case, either camera ex116 or computer ex111 may code the movingpicture data. In this case, an LSI ex117 included in computer ex111 orcamera ex116 performs coding processing. Note that software for codingand decoding may be integrated into a certain type of storage medium(such as a CD-ROM, a flexible disk and a hard disk) that is a recordingmedium readable by computer ex111 and the like. Furthermore,camera-equipped cellular phone ex115 may transmit a moving picture data.This moving picture data is data coded by an LSI included in cellularphone ex115.

In this content providing system ex100, content (e.g. a music livevideo) which has been taken by a user using camera ex113, camera ex116or the like is coded in the same manner as the above embodiment andtransmitted to streaming server ex103, while streaming server ex103distributes the content data to subscribers upon request. Thesubscribers here include computer ex111, PDA ex112, camera ex113,cellular phone ex114 and so on capable of decoding the above coded data.Content providing system ex100 with the above configuration is a systemthat enables the subscribers to receive and reproduce the coded data andrealizes personal broadcasting by allowing them to receive, decode andreproduce the data in real time.

The picture coding apparatus and the picture decoding apparatuspresented in the above embodiment can be used for coding and decoding tobe performed in each of the device constructing the above system.

An example for a cellular phone is described hereinafter.

FIG. 11 is a diagram showing cellular phone ex115 that employs thepicture coding method and the picture decoding method described in theabove embodiment. Cellular phone ex115 has an antenna ex201 fortransmitting/receiving radio waves to and from base station ex110, acamera unit ex203 such as a CCD camera capable of taking video and stillpictures, a display unit ex202 such as a liquid crystal display fordisplaying the decoded data, that are a video taken by camera unit ex203and a video received through antenna ex201 and the like, a main unitequipped with a group of operation keys ex204, a voice output unit ex208such as a speaker for outputting voices, a voice input unit ex205 suchas a microphone for inputting voices, a recording medium ex207 forstoring coded data or decoded data such as data of moving pictures orstill pictures taken by the camera, data of received e-mails and movingpicture data or still picture data, and a slot unit ex206 for enablingrecording medium ex207 to be attached to cellular phone ex115. Recordingmedium ex207 is embodied as a flash memory element, a kind of EEPROM(Electrically Erasable and Programmable Read Only Memory) that is anelectrically erasable and rewritable nonvolatile memory, stored in aplastic case such as an SD card.

Next, referring to FIG. 12, a description of cellular phone ex115 isgiven. In cellular phone ex115, a main control unit ex311 for centrallycontrolling display unit ex202 and each unit of the main unit having theoperation keys ex204 is configured in a manner in which a power supplycircuit unit ex310, an operation input control unit ex304, a picturecoding unit ex312, a camera interface unit ex303, an LCD (Liquid CrystalDisplay) control unit ex302, a picture decoding unit ex309, amultiplexing/demultiplexing unit ex308, a recording/reproducing unitex307, a modem circuit unit ex306 and a voice processing unit ex305 areinterconnected via a synchronous bus ex313.

When a call-end key or a power key is turned on by a user operation,power supply circuit unit ex310 supplies each unit with power from abattery pack, and activates camera-equipped digital cellular phone ex115to make it into a ready state.

In the cellular phone ex115, voice processing unit ex305 converts avoice signal received by the voice input unit ex205 in conversation modeinto digital voice data under the control of main control unit ex311comprised of a CPU, a ROM, a RAM and others, the modem circuit unitex306 performs spread spectrum processing on it, and a transmit/receivecircuit unit ex301 performs digital-to-analog conversion processing andfrequency transformation processing on the data, so as to transmit theresultant via antenna ex201. Also, in cellular phone ex115, datareceived by antenna ex201 in conversation mode is amplified andperformed of frequency transformation processing and analog-to-digitalconversion processing, modem circuit unit ex306 performs inverse spreadspectrum processing on the resultant, and voice processing unit ex305converts it into analog voice data, so as to output it via voice outputunit ex208.

Furthermore, when sending an e-mail in data communication mode, textdata of the e-mail inputted by operating operation keys ex204 on themain unit is sent out to main control unit ex311 via operation inputcontrol unit ex304. In main control unit ex311, after modem circuit unitex306 performs spread spectrum processing on the text data andtransmit/receive circuit unit ex301 performs digital-to-analogconversion processing and frequency transformation processing on it, theresultant is transmitted to base station ex110 via antenna ex201.

When picture data is transmitted in data communication mode, the picturedata taken by camera unit ex203 is supplied to picture coding unit ex312via camera interface unit ex303. When picture data is not to betransmitted, it is also possible to display such picture data taken bycamera unit ex203 directly on display unit ex202 via camera interfaceunit ex303 and LCD control unit ex302.

Picture coding unit ex312, which includes the picture coding apparatusaccording to the present invention, performs compression coding on thepicture data supplied from camera unit ex203 using the coding methodemployed by the picture coding apparatus presented in the aboveembodiment, so as to convert it into coded picture data, and sends itout to multiplexing/demultiplexing unit ex308. At this time, cellularphone ex115 sends voices received by voice input unit ex205 during theshooting by camera unit ex203, to multiplexing/demultiplexing unit ex308as digital voice data via voice processing unit ex305.

Multiplexing/demultiplexing unit ex308 multiplexes the coded picturedata supplied from picture coding unit ex312 and the voice data suppliedfrom voice processing unit ex305 using a predetermined method, modemcircuit unit ex306 performs spread spectrum processing on the resultingmultiplexed data, and the transmit/receive circuit unit ex301 performsdigital-to-analog conversion processing and frequency transformationprocessing on the resultant, so as to transmit the processed data viathe antenna ex201.

When receiving, in data communication mode, moving picture file datawhich is linked to a Web page or the like, modem circuit unit ex306performs inverse spread spectrum processing on the received signalreceived from base station ex110 via antenna ex201, and sends out theresulting multiplexed data to multiplexing/demultiplexing unit ex308.

In order to decode the multiplexed data received via antenna ex201,multiplexing/demultiplexing unit ex308 separates the multiplexed datainto a coded bitstream of picture data and a coded bitstream of voicedata, and supplies such coded picture data to picture decoding unitex309 and such voice data to voice processing unit ex305 via synchronousbus ex313.

Next, picture decoding unit ex309, which includes the picture decodingapparatus according to the present invention, decodes the codedbitstream of the picture data using the decoding method paired with thecoding method shown in the above-mentioned embodiment so as to generatemoving picture data for reproduction, and supplies such data to displayunit ex202 via LCD control unit ex302. Accordingly, moving picture dataincluded in the moving picture file linked to a Web page, for instance,is displayed. At the same time, voice processing unit ex305 converts thevoice data into an analog voice signal, and then supplies this to voiceoutput unit ex208. Accordingly, voice data included in the movingpicture file linked to a Web page, for instance, is reproduced.

Note that the abovementioned system is not an exclusive example andtherefore that at least either the picture coding apparatus or thepicture decoding apparatus of the above embodiment can be incorporatedinto a digital broadcasting system as shown in FIG. 13, in acircumstance that satellite/terrestrial digital broadcasting has been arecent topic of conversation. To be more specific, at a broadcastingstation ex409, a coded bitstream of video information is transmitted, byradio waves, to a satellite ex410 for communications or broadcasting.Upon receipt of it, broadcast satellite ex410 transmits radio waves forbroadcasting, an antenna ex406 of a house equipped with satellitebroadcasting reception facilities receives such radio waves, and anapparatus such as a television (receiver) ex401 and a set top box (STP)ex407 decodes the coded bitstream and reproduces the decoded data. Thepicture decoding apparatus as shown in the above-mentioned embodimentcan be performed in reproduction apparatus ex403 for reading anddecoding the coded bitstream recorded on a storage medium ex402 that isa recording medium such as a CD and a DVD. In this case, a reproducedvideo signal is displayed on a monitor ex404. It is also conceivablethat the picture decoding apparatus is performed in the set top boxex407 connected to a cable ex405 for cable television or the antennaex406 for satellite/terrestrial broadcasting so as to reproduce it on atelevision monitor ex408. In this case, the picture decoding apparatusmay be incorporated into the television, not in the set top box. Or, acar ex412 with an antenna ex411 can receive a signal from satelliteex410, base station ex107 or the like, so as to reproduce a movingpicture on a display device such as a car navigation system ex413mounted on car ex412.

Furthermore, it is also possible to code a picture signal by the picturecoding apparatus presented in the above embodiment and to record theresultant on a recording medium. Examples include a DVD recorder forrecording a picture signal on a DVD disc ex421 and a recorder ex420 suchas a disc recorder for recording a picture signal on a hard disk.Moreover, a picture signal can also be recorded in an SD card ex422. Ifthe recorder ex420 is equipped with the picture decoding apparatuspresented in the above embodiment, it is possible to reproduce a picturesignal recorded on DVD disc ex421 or in SD card ex422, and display it onmonitor ex408.

As the configuration of the car navigation system ex413, theconfiguration without camera unit ex203 and the camera interface unitex303, out of the configuration shown in FIG. 12, is conceivable. Thesame is applicable to computer ex111, television (receiver) ex401 andthe like.

Concerning the terminals such as cellular phone ex114, atransmitting/receiving terminal having both a coder and a decoder, aswell as a transmitting terminal only with a coder, and a receivingterminal only with a decoder are the three possible forms substantially.

As stated above, it is possible to employ the picture coding method andthe picture decoding method presented in the above embodiment into anyone of the above-mentioned devices and systems. Accordingly, it becomespossible to achieve an effect described in the abovementionedembodiment.

As mentioned hereinbefore, it is possible to code the output area codinginformation CropData with less number of bits without deterioratingaccuracy of output pixel to be presented, and the practical value ishigh.

Note that each function block in the block diagram shown in FIG. 5 andFIG. 6 can be realized as an LSI that is an integrated circuit apparatustypically. Such LSI may be incorporated in one or plural chips e.g.,function blocks other than a memory may be incorporated into a singlechip. Here, LSI is exemplified, however, it may be called as “IC”,“system LSI”, “super LSI” and “ultra LSI” depending on the integrationdegree.

The method for incorporation into an integrated circuit is not limitedto the LSI, and it may be realized with an exclusive line or a generalprocessor. After manufacturing of LSI, a Field Programmable Gate Array(FPGA) that is programmable, or a reconfigurable processor that canreconfigure the connection and settings for the circuit cell in the LSI,may be utilized.

Furthermore, along with the arrival of technique for incorporation intoan integrated circuit, which replaces the LSI owing to a progress insemiconductor technology or another extended technique, integration ofthe function blocks may be carried out using the newly-arrivedtechnology. Application of bio-technology may be cited as one of theexamples.

And also in each function block, a unit to store data may be structuredindividually as an record medium in the embodiment and not necessary tobe a chip.

In each function block of block diagrams shown in FIG. 5 and FIG. 6, andthe flowcharts shown in FIG. 7A, FIG. 7B, FIG. 8A and FIG. 8B, theessential part is realized by a micro processor and a program, thepresent invention, therefore, may be constructed as a program.

Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to be notedthat various changes and modifications will be apparent to those skilledin the art. Therefore, unless otherwise such changes and modificationsdepart from the scope of the present invention, they should be construedas being included therein.

The invention claimed is:
 1. A picture coding apparatus comprising: apicture coding unit operable to code a picture signal; a ratio codingunit operable to code a ratio of a number of luminance pixels to anumber of chrominance pixels for the picture signal; a selecting unitoperable to select one coding method out of at least two coding methods,the one coding method being selected based on the ratio; and a datacoding unit operable to code data related to a picture size inaccordance with the selected coding method, wherein the data related tothe picture size indicates a size of a picture corresponding to thepicture signal, and wherein, when a ratio of a number of verticalluminance pixels to a number of vertical chrominance pixels is N:1, saidselecting unit selects a coding method coding 1/N of a number ofvertical pixels, the vertical luminance pixels and the verticalchrominance pixels being included in the picture signal.
 2. A picturecoding method comprising: coding, using a processor, a picture signal;coding a ratio of a number of luminance pixels to a number ofchrominance pixels for the picture signal; selecting one coding methodout of at least two coding methods, the one coding method being selectedbased on the ratio; and coding data related to a picture size inaccordance with the selected coding method, wherein the data related tothe picture size indicates a size of a picture corresponding to thepicture signal, and wherein, when a ratio of a number of verticalluminance pixels to a number of vertical chrominance pixels is N:1, saidselecting selects a coding method coding 1/N of a number of verticalpixels, the vertical luminance pixels and the vertical chrominancepixels being included in the picture signal.